stlcamaros

Hi Everyone,

This is my first post here so go easy on me! I've already been finding a ton of useful information but I am stumped on my current problem.

Here it is....

I recently purchased a very used 1989 Iroc Z 350. The guy I got it from put a different 350 in it and then sold it to me. It still has the TPI on it. He couldn't get the engine running right and got frustrated with it. It's running very poorly and I am in the process of getting another engine ready to swap into it, so it's not a huge deal to me but.......

In the meantime.......I am trying to sort out an issue with the TPS voltage and hopefully someone can help. I'm hoping to get it running good enough to drive until I get the other engine built......I have searched and did not find the specifics linked to my kind of problem. The problem is that I can not get the TPS voltage to adjust within spec. When I try to set it (key on engine not running) the TPS voltage at idle reads like 123 MV (milivots) Any position I move it to I can not get it in the range of the required .55 volts. It won't adjust properly at all. And the most I can get out of it when it's turned to WOT is like 1.4 Volts. No matter what position I adjust it to I can not get the idle voltage in the range of .55 volts......I read on here that it could be related to a grounding problem?????? Can anyone provide any input on this problem if you know of a solution to a similar problem from past experiences???? Please let me know and I greatly appreciate the input....

Thanks, Dean

stlcamaros

WOW.....not even a welcome aboard from anyone??????

NINÅ

1981LT1

iTrader: (1)

Welcom aboard. I agree. You need to make sure you are getting 5 volts at the grey wire. If you are, it's possible you have a bad TPS. Also, trace the gound and make sure it is secure. Bad grounds are probably 90% of the electrical problems. If both of these check out, I would bet money on a bad TPS.

1981LT1

iTrader: (1)

Dont forget to check the ground point on the back of the head. If this is broken or corroded, fix it immidiately. This will most llikely fix all of your problems if it isn't correct.

stlcamaros

I forgot to mention in my original post.....I have a new TPS along with the old one. Both TPS' do the same thing when hooked up. The grey wire has 5 volts going to the TPS plug. The black wire has .29 milivots of voltage with the key on. Should it have anything???? I hate electrical problems! I guess I will have to try and trace it down to possibly a ground problem. I did check the ground to the head and it is in tact, at least it appears to be..........Any input?

Thanks.

1981LT1

iTrader: (1)

You can do a quick and dirty test by stripping a little insulation off the black wire and splicing another wire straight to ground. This will rule out any ground issues. Get back with the results. Electrical problems are a huge pita but they are usually very simple to fix. You either have a power or ground problem. It is very rarely anything different.

stlcamaros

This is a good idea. Will try that and let you know the results. Thanks for the suggestion.

Dean

stlcamaros

I just tried it and it still didn't work out. I connected a ground to a bolt on the body to the black wire, still no go. The blue wire was reading 6.4 milivots coming out with the key on. At WOT showing only 1.4 volts. The car stumbles and won't idle right. It also won't take the gas when you give it throttle. Without the jumper ground wire connected, the black wire was showing 24.5 milivots. If it is the ground shouldn't it not be showing any voltage at all??????

1981LT1

iTrader: (1)

When you are measuring the voltage are you using a dvom? If so, the tps need tone plugged into the throttle body with the ignition turned on but not running. Make sure the ground lead is on a good ground and stick the other probe into the back of the grey wire. This must be 5 volts. Then, with your dvom set to 20 volts, probe the back of the blue wire. This should be somewhere around .5 volts. Then start to open the tb and watch the voltage. If it doesn't climb, and you know it's seated correctly in the tb, then it has to be a bad sensor.